Linear Power Supply and Switching Power Supply

(1) Concepts

A Linear Power Supply typically samples the output voltage and sends it to the Compare voltage amplifier with the reference voltage. The output of this voltage amplifier serves as the input of the Voltage Adjustment tube, it is used to control the adjustment tube so that its junction voltage changes with the input, so as to adjust its output voltage. However, the switching power supply changes the output voltage by changing the switch-on and off time, that is, the duty cycle. The main working principle of the switching power supply is to turn on the mos of the upper and lower bridges in turn, so it is repeated, because the MOs are switched in turn, so it is called the switching power supply. As follows:

(2) Comparison
The linear power supply has no switch intervention, so that the upper pipe is always in the water, if there are more, it will leak out, this is what we often see some Linear Power Supply of MOS Tube Heat is very large, all unused power is converted into heat energy. From this point of view, the conversion efficiency of linear power supply is very low, and when the heat is high, the life of the component is bound to decrease, affecting the final use effect.
The linear power device is working in a linear state. That is to say, when used, the power device is always working, which leads to a low working efficiency, generally between 50% and ~ 60%, he is a good linear power supply. In this way, his volume is very large, heavy, low efficiency, and great heat. He also has his advantages: small ripple, good adjustment rate, and small external interference. Suitable for use with analog circuits, various types of amplifiers, etc.

Switch power supply. The power device is working on or off the switch. (The switching frequency is very fast when the power device is on or off. The general flat-panel Switching Power Supply frequency is between 100 and ~ 200 kHz, module power supply in 300 ~ 500 kHz ). In this way, the loss will be small, and the efficiency will be high. The transformer also needs to be made of materials with high permeability. Efficiency: 80% ~ 90%, it is said that the best vicor module in the United States is as high as 99%. The efficiency of the switching power supply is small, but the voltage and current adjustment rate is discounted compared with the linear power supply.

(3) Summary

A low dropout regulator is a low-voltage differential linear voltage regulator, which is relative to a traditional linear voltage regulator. Traditional Linear Voltage Regulators Require that the input voltage be 2 V higher than the output voltage ~ 3 V or above, otherwise it will not work normally. However, in some cases, such conditions are obviously too harsh. In this case, the power conversion chip of the ldos class is available.
Dcdc refers to DC (to) DC (conversion of different DC power supply values). It is a switch that can be called dcdc converter as long as it complies with this definition. However, the general saying is that the device that implements DC-to-DC switch is called dcdc.
In terms of usage, dcdc is used in scenarios with a large pressure drop, but it is easy to produce interference and the speed is fast. The ldos is used in scenarios with a small pressure drop, but with little interference.